Apparatus for measuring insulation resistance

ABSTRACT

An apparatus for measuring an insulation resistance according to the present invention includes: a first distribution resistor connected to a positive terminal of a battery and a ground; a first switch connected to the positive terminal of the battery and the first distribution resistor; a second distribution resistor connected to a negative terminal of the battery and the ground; a second switch connected to the negative terminal of the battery and the second distribution resistor; and an insulation resistance measurement unit measuring a resistance value of a negative electrode insulation resistor of the battery using a first voltage applied to the first distribution resistor and measuring a resistance value of a positive electrode insulation resistor of the battery using a second voltage applied to the second distribution resistor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/815,777 filed on Mar. 11, 2020, which claims benefits of priority ofKorean Patent Application No. 10-2019-0029760 filed on Mar. 15, 2019.The disclosure of each of the foregoing application is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The following disclosure relates to an apparatus for measuring aninsulation resistance having a simple configuration for measuring aninsulation resistance of a battery and improving insulation resistancemeasurement rate.

BACKGROUND

In an electric vehicle or a hybrid vehicle using a high-voltage battery,an insulation resistance of the battery is very important because theinsulation resistance indicates that a ground fault has occurred. Apositive electrode insulation resistor between a positive terminal ofthe battery and a ground (e.g., a chassis ground of a vehicle) and anegative electrode insulation resistor between a negative terminal ofthe battery and the ground have infinite resistance values when noground fault occurs, but have small resistance values when a groundfault occurs.

The insulation resistance of the battery is measured by using a voltageapplied to a distribution resistor after forming a current path that isconnected to the positive terminal of the battery, the ground, and thenegative terminal of the battery.

In a conventional apparatus for measuring an insulation resistance, anoperational amplifier is provided to measure a voltage applied to adistribution resistor and a test circuit is provided to test theperformance of the operational amplifier. When the operational amplifierand the test circuit are provided in the apparatus for measuring aninsulation resistance, this results in increases in the complexity andthe price of the apparatus, and a decrease in an insulation resistancemeasurement rate. In a conventional apparatus for measuring aninsulation resistance, only a distribution resistor is connected to theground. In this case, a switch is not protected from an external surge,thereby shortening the lifespan of the apparatus.

RELATED ART DOCUMENT

[Patent Document]

KR 2013-0059107A (Jun. 5, 2013)

SUMMARY

An embodiment of the present invention is directed to providing anapparatus for measuring an insulation resistance improving insulationresistance measurement rate, while the complexity and the price of theapparatus are reduced.

Another embodiment of the present invention is directed to providing anapparatus for measuring an insulation resistance capable of protecting aswitch from an external surge, so that the lifespan of the apparatus canbe extended.

In one general aspect, an apparatus for measuring an insulationresistance includes: a first distribution resistor connected to apositive terminal of a battery and a ground; a first switch connected tothe positive terminal of the battery and the first distributionresistor; a second distribution resistor connected to a negativeterminal of the battery and the ground; a second switch connected to thenegative terminal of the battery and the second distribution resistor;and an insulation resistance measurement unit measuring a resistancevalue of a negative electrode insulation resistor of the battery using afirst voltage applied to the first distribution resistor and measuring aresistance value of a positive electrode insulation resistor of thebattery using a second voltage applied to the second distributionresistor.

The insulation resistance measurement unit may be connected directly tothe first distribution resistor and the second distribution resistor tomeasure the first voltage and the second voltage.

The insulation resistance measurement unit may control the first switchand the second switch to be turned on or off to create a current pathconnected to the positive terminal of the battery, the ground, and thenegative terminal of the battery.

When the resistance value of the positive electrode insulation resistorof the battery is measured, the insulation resistance measurement unitmay operate the first switch in a turn-off state and the second switchin a turn-on state. When the resistance value of the negative electrodeinsulation resistor of the battery is measured, the insulationresistance measurement unit may operate the first switch in a turn-onstate and the second switch in a turn-off state.

When the resistance value of the positive electrode insulation resistorof the battery is measured, the insulation resistance measurement unitmay assume the negative electrode insulation resistor of the battery tohave an infinite resistance value. When the resistance value of thenegative electrode insulation resistor of the battery is measured, theinsulation resistance measurement unit may assume the positive electrodeinsulation resistor of the battery to have an infinite resistance value.

The apparatus for measuring an insulation resistance may furtherinclude: a first protective resistor connected to the positive terminalof the battery and the first switch; and a second protective resistorconnected to the negative terminal of the battery and the second switch.

The apparatus for measuring an insulation resistance may further includea direct current voltage source connected to the second distributionresistor and the ground.

The insulation resistance measurement unit may measure the resistancevalue of the positive electrode insulation resistor of the batterythrough the following Equation 1.

$\begin{matrix}{{{Riso}\; 1} = {{( \frac{{Vb} - {Vdc}}{V\; 2} )R\; 2} - ( {{R\; 2} + {{Ron}\; 2}} )}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

(where Riso1 is the resistance value of the positive electrodeinsulation resistor of the battery, Vb is a voltage of the battery, Vdcis a voltage of the direct current voltage source, V2 is the secondvoltage applied to the second distribution resistor, R2 is a resistancevalue of the second distribution resistor, and Ron2 is a resistancevalue of the second protective resistor).

The insulation resistance measurement unit may measure the resistancevalue of the negative electrode insulation resistor of the batterythrough the following Equation 2.

$\begin{matrix}{{{Riso}\; 2} = {{\frac{Vb}{V\; 1}R\; 1} - ( {{R\; 1} + {{Ron}\; 1}} )}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

(where Riso2 is the resistance value of the negative electrodeinsulation resistor of the battery, Vb is a voltage of the battery, V1is the first voltage applied to the first distribution resistor, R1 is aresistance value of the first distribution resistor, and Ron1 is aresistance value of the first protective resistor).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an apparatus formeasuring an insulation resistance according to an exemplary embodimentof the present invention.

FIG. 2 is a diagram schematically illustrating a case in which adielectric breakdown occurs at a positive electrode of the battery inFIG. 1.

FIG. 3 is a diagram schematically illustrating a case in which adielectric breakdown occurs at a negative electrode of the battery inFIG. 1.

DETAILED DESCRIPTION OF MAIN ELEMENTS

-   -   10: Battery    -   110: Positive electrode insulation resistor    -   120: Negative electrode insulation resistor    -   130: First distribution resistor    -   140: First switch    -   150: Second distribution resistor    -   160: Second switch    -   170: First protective resistor    -   180: Second protective resistor    -   190: Direct current voltage source    -   200: Insulation resistance measurement unit

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an apparatus for measuring an insulation resistanceaccording to the present invention will be described in detail withreference to the accompanying drawings. The accompanying drawings areprovided merely for illustrative purposes so as to sufficiently transferthe spirit of the present invention to those skilled in the art, and thepresent invention is not limited to the accompanying drawings set forthbelow, but may be implemented in other forms.

FIG. 1 is a diagram schematically illustrating an apparatus formeasuring an insulation resistance according to an exemplary embodimentof the present invention.

The apparatus for measuring an insulation resistance according to anexemplary embodiment of the present invention includes a firstdistribution resistor 130, a first switch 140, a second distributionresistor 150, a second switch 160, and an insulation resistancemeasurement unit 200.

The first distribution resistor 130 is connected to a positive terminalof a battery 10 and a ground, and the first switch 140 is connected tothe positive terminal of the battery 10 and the first distributionresistor 130. The second distribution resistor 150 is connected to anegative terminal of the battery 10 and the ground, and the secondswitch 160 is connected to the negative terminal of the battery 10 andthe second distribution resistor 150. Here, the battery 10 may include aplurality of battery cells connected in series or in parallel.

The insulation resistance measurement unit 200 is connected directly tothe first distribution resistor 130 and the second distribution resistor150 to measure a first voltage applied to the first distributionresistor 130 and a second voltage applied to the second distributionresistor 150. Here, the direct connections of the insulation resistancemeasurement unit 200 to the first distribution resistor 130 and to thesecond distribution resistor 150 means connections between theinsulation resistance measurement unit 200 and the first distributionresistor 130 and between the insulation resistance measurement unit 200and the second distribution resistor 150 without any interveningcomponents.

In a conventional apparatus for measuring an insulation resistance, anoperational amplifier and a test circuit for testing the performance ofthe operational amplifier are provided between an insulation resistancemeasurement unit and a distribution resistor. However, when theoperational amplifier or the test circuit is provided in the apparatusfor measuring an insulation resistance, this results in increases in thecomplexity and the price of the apparatus, and an insulation resistancemeasurement rate decreases because it is required to add a process ofprocessing a voltage that is amplified by the operational amplifier tothe insulation resistance measurement unit. In contrast, the presentinvention is capable of not only decreasing the complexity and the priceof the apparatus for measuring an insulation resistance but alsoimproving the insulation resistance measurement rate by connecting theinsulation resistance measurement unit 200 directly to the firstdistribution resistor 130 and the second distribution resistor 150 whileexcluding an intervening component such as an operational amplifier or atest circuit.

Meanwhile, the insulation resistance measurement unit 200 measures aresistance value of a negative electrode insulation resistor 120 of thebattery 10 using the first voltage applied to the first distributionresistor 130, and measures a resistance value of a positive electrodeinsulation resistor 110 of the battery 10 using the second voltageapplied to the second distribution resistor 150, as will be describedbelow. Here, the second voltage measured by the insulation resistancemeasurement unit 200 may refer only to a voltage applied to the seconddistribution resistor 150 as illustrated in FIG. 2, but may optionallyrefer to a voltage applied between one end of the second distributionresistor 150 (that is, a point between the second distribution resistor150 and the second switch 160) and the ground.

In order for the insulation resistance measurement unit 200 to measurethe resistance values of the positive electrode insulation resistor 110and the negative electrode insulation resistor 120 of the battery 10, itis required to create a current path connected to the positive terminalof the battery 10, the ground, and the negative terminal of the battery10. To do this, the insulation resistance measurement unit 200 alsoserves to control the first switch 140 and the second switch 160 to beturned on or off so as to create a current path.

In order to measure voltages applied to the distribution resistors 130and 150, measure insulation resistances of the battery 10 using themeasured voltages, and control the switches 140 and 160 to create acurrent path, the insulation resistance measurement unit 200 includes amicro controller unit (MCU).

According to FIG. 1, the first distribution resistor 130 is locatedbetween the first switch 140 and the ground, and the second distributionresistor 150 is located between the second switch 160 and the ground.However, when the distribution resistors 130 and 150 are located onlybetween the switches 140 and 160 and the ground as described above,there is concern that the switches 140 and 160 would not be protectedfrom external surges, which may shorten the lifespan of the apparatus.Accordingly, it is preferable in terms of the lifespan extension of theapparatus to arrange a first protective resistor 170 connected to thepositive terminal of the battery 10 and the first switch 140 and asecond protective resistor 180 connected to the negative terminal of thebattery 10 and the second switch 160, thereby protecting the switches140 and 160 from external surges.

FIG. 1 illustrates that the first protective resistor 170 is disposedbetween the positive terminal of the battery 10 and the first switch140, but the first protective resistor 170 may be disposed between thefirst switch 140 and the first distribution resistor 130. Alternatively,the first protective resistor 170 may be disposed both between thepositive terminal of the battery 10 and the first switch 140 and betweenthe first switch 140 and the first distribution resistor 130. Likewise,although FIG. 1 illustrates that the second protective resistor 180 isdisposed between the negative terminal of the battery 10 and the secondswitch 160, the second protective resistor 180 may be disposed betweenthe second switch 160 and the second distribution resistor 150.Alternatively, the second protective resistor 180 may be disposed bothbetween the negative terminal of the battery 10 and the second switch160 and between the second switch 160 and the second distributionresistor 150.

In addition, when the insulation resistance measurement unit 200measures the second voltage applied to the second distribution resistor150, in order to adjust a range of the second voltage, morespecifically, to obtain a value of the second voltage other than zero(0), it is preferable to arrange a direct current voltage source 190connected to the second distribution resistor 150 and the ground. Here,a voltage value of the direct current voltage source 190 may be positive(+) or negative (−).

FIG. 2 is a diagram schematically illustrating a case in which adielectric breakdown occurs at the positive electrode of the battery inFIG. 1.

As illustrated in FIG. 2, when the dielectric breakdown occurs at thepositive electrode of the battery 10, the positive electrode insulationresistor 110 between the positive terminal of the battery 10 and theground has a specific value rather than an infinite value. Accordingly,in order to check whether or not a dielectric breakdown occurs at thepositive electrode of the battery 10, the insulation resistancemeasurement unit 200 operates the first switch 140 in a turn-off stateand the second switch 160 in a turn-on state.

When the resistance value of the positive electrode insulation resistor110 of the battery 10 is measured, the insulation resistance measurementunit 200 assumes the negative electrode insulation resistor of thebattery 10 to have an infinite resistance value. If the negativeelectrode insulation resistor is assumed to have an infinite resistancevalue, the insulation resistance measurement unit 200 may measure theresistance value of the positive electrode insulation resistor 110 ofthe battery 10 by merely measuring only one, i.e. the second voltage,not through simultaneous equations, as will be described below, therebyenabling rapid measurement.

When the first switch 140 is operated in the turn-off state and thesecond switch 160 is operated in the turn-on state, a current path isformed in such a manner as to be connected to the positive terminal ofthe battery 10, the positive electrode insulation resistor 110, theground, the second distribution resistor 150, the second protectiveresistor 180, and the negative terminal of the battery 10.

When a current I2 flows through the current path formed at the time ofthe dielectric breakdown at the positive electrode of the battery 10,the current I2 is represented by the following Equation 1.

$\begin{matrix}{{I\; 2} = \frac{{Vb} - {Vdc}}{{{Riso}\; 1} + {R\; 2} + {{Ron}\; 2}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In Equation 1, Vb denotes a voltage of the battery 10, Vdc denotes avoltage of the direct current voltage source 190, Riso1 denotes theresistance value of the positive electrode insulation resistor 110 ofthe battery, R2 denotes a resistance value of the second distributionresistor 150, and Ron2 denotes a resistance value of the secondprotective resistor 180.

If the current I2 is as shown in Equation 1, the second voltage V2applied to the second distribution resistor 150 is represented by thefollowing Equation 2.

$\begin{matrix}{{V\; 2} = {{I\; 2 \times R\; 2} = {\frac{R\; 2}{{{Riso}\; 1} + {R\; 2} + {{Ron}\; 2}}( {{Vb} - {Vdc}} )}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

When Equation 2 is solved with respect to Riso1, then the followingEquation 3 is obtained.

$\begin{matrix}{{{Riso}\; 1} = {{( \frac{{Vb} - {Vdc}}{V\; 2} )R\; 2} - ( {{R\; 2} + {{Ron}\; 2}} )}} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

The insulation resistance measurement unit 200 may include a memory onwhich a voltage of the battery 10, a voltage of the direct currentvoltage source 190, a resistance value of the second distributionresistor 150, and a resistance value of the second protection resistor180 are stored. Accordingly, the insulation resistance measurement unit200 may measure the resistance value of the positive electrodeinsulation resistor 110 by merely measuring the second voltage appliedto the second distribution resistor 150.

FIG. 3 is a diagram schematically illustrating a case in which adielectric breakdown occurs at the negative electrode of the battery inFIG. 1.

As illustrated in FIG. 3, when the dielectric breakdown occurs at thenegative electrode of the battery 10, the negative electrode insulationresistor 120 between the negative terminal of the battery 10 and theground has a specific value rather than an infinite value. Accordingly,in order to check whether or not a dielectric breakdown occurs at thenegative electrode of the battery 10, the insulation resistancemeasurement unit 200 operates the first switch 140 in a turn-on stateand the second switch 160 in a turn-off state.

When the resistance value of the negative electrode insulation resistor120 of the battery 10 is measured, the insulation resistance measurementunit 200 assumes the positive electrode insulation resistor of thebattery 10 to have an infinite resistance value. If the positiveelectrode insulation resistor is assumed to have an infinite resistancevalue, the insulation resistance measurement unit 200 may measure theresistance value of the positive electrode insulation resistor 120 ofthe battery 10 by merely measuring only one, i.e. the first voltage, notthrough simultaneous equations, as will be described below, therebyenabling rapid measurement.

When the first switch 140 is operated in the turn-on state and thesecond switch 160 is operated in the turn-off state, a current path isformed in such a manner as to be connected to the positive terminal ofthe battery 10, the first protective resistor 170, the firstdistribution resistor 130, the ground, the negative electrode insulationresistor 120, and the negative terminal of the battery 10.

When a current I1 flows through the current path formed at the time ofthe dielectric breakdown at the negative electrode of the battery 10,the current I1 is represented by the following Equation 4.

$\begin{matrix}{{I\; 1} = \frac{Vb}{{{Ron}\; 1} + {R\; 1} + {{Riso}\; 2}}} & \lbrack {{Equation}\mspace{14mu} 4} \rbrack\end{matrix}$

In Equation 4, Vb denotes a voltage of the battery 10, Ron1 denotes aresistance value of the first protective resistor 170, R1 denotes aresistance value of the first distribution resistor 130, and Riso2denotes a resistance value of the negative electrode insulation resistor120 of the battery.

If the current I1 is as shown in Equation 4, the first voltage V1applied to the first distribution resistor 130 is represented by thefollowing Equation 5.

$\begin{matrix}{{V\; 1} = {{I\; 1 \times R\; 1} = {\frac{R\; 1}{{{Ron}\; 1} + {R\; 1} + {{Riso}\; 2}}{Vb}}}} & \lbrack {{Equation}\mspace{14mu} 5} \rbrack\end{matrix}$

When Equation 5 is solved with respect to Riso2, then the followingEquation 6 is obtained.

$\begin{matrix}{{{Riso}\; 2} = {{\frac{Vb}{V\; 1}R\; 1} - ( {{R\; 1} + {{Ron}\; 1}} )}} & \lbrack {{Equation}\mspace{14mu} 6} \rbrack\end{matrix}$

The insulation resistance measurement unit 200 may include a memory onwhich a voltage of the battery 10, a resistance value of the firstdistribution resistor 130, and a resistance value of the firstprotective resistor 170 are stored. Accordingly, the insulationresistance measurement unit 200 may measure the resistance value of thenegative electrode insulation resistor 120 by merely measuring the firstvoltage applied to the first distribution resistor 130.

As described above, the apparatus for measuring an insulation resistanceaccording to an exemplary embodiment of the present invention excludesan intervening component such as an operational amplifier or a testcircuit, so that the apparatus can be simplified and the price of theapparatus can be reduced, and the insulation resistance measurement ratecan be improved. In addition, when a resistance value of the positiveelectrode insulation resistor 110 of the battery 10 is measured, it isassumed that the negative electrode insulation resistor of the battery10 has an infinite resistance value, and when a resistance value of thenegative electrode insulation resistor 120 of the battery 10 ismeasured, it is assumed that the positive electrode insulation resistorof the battery 10 has an infinite resistance value, thereby furtherimproving the insulation resistance measurement rate.

According to the present invention, it is possible to not only simplifythe apparatus for measuring an insulation resistance of a battery andreduce the price of the apparatus but also improve an insulationresistance measurement rate by excluding an intervening component suchas an operational amplifier or a test circuit.

In addition, it is possible to protect the switches from external surgesby placing the first protective resistor connected to the positiveterminal of the battery and the first switch and the second protectiveresistor connected to the negative terminal of the battery and thesecond switch. Accordingly, it is possible to extend the life of theapparatus.

Although the present invention has been described with reference to thespecific exemplary embodiments and the accompanying drawings, thepresent invention is not limited to the above-described exemplaryembodiments but may be variously modified and changed from the abovedescription by those skilled in the art to which the present inventionpertains. Therefore, the spirit of the present invention should beunderstood only by the following claims, and all of the equivalences orequivalent modifications to the claims are intended to fall within thescope of the technical idea of the present invention.

What is claimed is:
 1. An apparatus for measuring an insulationresistance, the apparatus comprising: a first distribution resistorcoupled to a positive terminal of a battery and a ground; a first switchcoupled to the positive terminal of the battery and the firstdistribution resistor; a second distribution resistor coupled to anegative terminal of the battery and the ground; a second switch coupledto the negative terminal of the battery and the second distributionresistor; and an insulation resistance measurement unit measuring anegative electrode insulation resistance and a positive electrodeinsulation resistance of the battery, wherein a first voltage is appliedto the first distribution resistor and a second voltage is applied tothe second distribution resistor according to an operation of the firstswitch and the second switch, and wherein the insulation resistancemeasurement unit measures only the first voltage among the first voltageand the second voltage and measures the negative electrode insulationresistance of the battery based on the first voltage, and the insulationresistance measurement unit measures only the second voltage among thefirst voltage and the second voltage and measures the positive electrodeinsulation resistance of the battery based on the second voltage.
 2. Theapparatus for measuring an insulation resistance of claim 1, whereinwhen the resistance value of the positive electrode insulation resistorof the battery is measured, the insulation resistance measurement unitoperates the first switch in a turn-off state and the second switch in aturn-on state, and when the resistance value of the negative electrodeinsulation resistor of the battery is measured, the insulationresistance measurement unit operates the first switch in turn-on stateand the second switch in a turn-off state.
 3. The apparatus of claim 1,wherein when measuring the negative electrode insulation resistance ofthe battery, the insulation resistance measurement unit does not use thesecond voltage while using the first voltage, and when measuring thepositive electrode insulation resistance of the battery, the insulationresistance measurement unit does not use the first voltage while usingthe second voltage.
 4. The apparatus for measuring an insulationresistance of claim 1, further comprising: a first protective resistorcoupled to the positive terminal of the battery and the first switch; asecond protective resistor coupled to the negative terminal of thebattery and the second switch; a direct current voltage source coupledto the second distribution resistor and the ground.
 5. The apparatus formeasuring an insulation resistance of claim 4, wherein the insulationresistance measurement unit include a memory on which a voltage of thebattery, a voltage of the direct current voltage source, a resistancevalue of the first distribution resistor, a resistance value of thefirst protection resistor, a resistance value of the second distributionresistor, and a resistance value of the second protection resistor arestored.
 6. The apparatus for measuring an insulation resistance of claim4, wherein the insulation resistance measurement unit measures theresistance value of the positive electrode insulation resistor of thebattery through the following Equation 1:${{Riso}\; 1} = {{( \frac{{Vb} - {Vdc}}{V\; 2} )R\; 2} - ( {{R\; 2} + {{Ron}\; 2}} )}$where Riso1 is the resistance value of the positive electrode insulationresistor of the battery, Vb is a voltage of the battery, Vdc is avoltage of the direct current voltage source, V2 is the second voltageapplied to the second distribution resistor, R2 is a resistance value ofthe second distribution resistor, and Ron2 is a resistance of the secondprotective resistor.
 7. The apparatus for measuring an insulationresistance of claim 4, wherein the insulation resistance measurementunit measures the resistance value of the negative electrode insulationresistor of the battery through the following Equation 2:${{Riso}\; 2} = {{( \frac{Vb}{V\; 1} )R\; 1} - ( {{R\; 1} + {{Ron}\; 1}} )}$where Riso2 is the resistance value of the negative electrode insulationresistor of the battery, Vb is a voltage of the battery, V1 is the firstvoltage applied to the first distribution resistor, R1 is a resistancevalue of the first distribution resistor, and Ron1 is a resistance valueof the first protective resistor.